If you’re seeing the dreaded “Service Trailer Brake System” message on your dash, you’re not alone. As a technician with over two decades of experience, I’ve seen this issue countless times on otherwise solid GM trucks. It’s often a sign that your factory Trailer Brake Control Module (TBCM) has failed, usually due to its exposed location on the frame where it battles moisture, road salt, and vibrations. This isn’t just an annoying light; it’s a critical safety failure that compromises your ability to safely stop while towing.
This is the definitive, hassle-free solution. We are offering a genuine GM Trailer Brake Control Module, part number 20964299 (also replaces 20850923), that arrives at your doorstep fully programmed to your vehicle’s specific VIN. We flash it with the latest, most stable software directly from GM before it ships. This means you can bypass the expensive and time-consuming trip to the dealership for programming. You get a part that is truly plug-and-play, restoring full, reliable function to your trailer braking system.
Is Your Truck Showing These Symptoms?
- ✔ Persistent “Service Trailer Brake System” warning on the Driver Information Center (DIC).
- ✔ “Trailer Connected” or “Trailer Disconnected” messages appearing randomly, even without a trailer.
- ✔ The manual trailer brake slide switch is unresponsive or works intermittently.
- ✔ No power output to the trailer’s electric brakes, confirmed with a tester.
- ✔ Diagnostic Trouble Codes (DTCs) stored in the system, such as C0277, U0100, or other communication-related faults.
Case Study: A Tricky Diagnosis
I had a 2013 Silverado 2500 in the shop last winter. The owner was frustrated because his trailer brakes would work fine for 20 minutes, then cut out completely, only to start working again after the truck sat overnight. Other shops couldn’t find the issue. I suspected the TBCM. Once I got it on the lift, I saw the problem immediately. The module’s casing had a hairline crack, and years of salty winter roads had allowed moisture inside, corroding the circuit board. This caused the intermittent failure that was so hard to pin down. Replacing the module with a properly sealed and programmed unit like this one solved his problem for good.
A Straightforward Guide to Installation
Installing your new 2013 Yukon XL 2500 TBCM is a job most DIYers can handle in under an hour with basic hand tools. The module is typically located on the driver’s side frame rail.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the Module: On SUVs like the Yukon XL 2500 and Suburban 2500, find the module on the left-hand (driver’s side) frame rail, roughly in the middle. For Sierra and Silverado pickups, it’s typically on the left-hand rear section of the frame, near the spare tire.
- Disconnect Electrical Connectors: Carefully press the release tabs on the two electrical connectors and pull them straight out from the module. Inspect the connectors for any corrosion and clean if necessary.
- Remove the Old Module: Use a socket wrench to remove the bolts or nuts securing the TBCM to the frame bracket. The old module should now come free.
- Install the New Module: Mount your new, pre-programmed TBCM onto the frame bracket and tighten the fasteners securely.
- Reconnect and Finalize: Plug the two electrical connectors firmly back into the new module until they click. Reconnect your battery’s negative terminal. Start the vehicle; the “Service Trailer Brake System” message should be gone, and your system is ready for use.
Guaranteed Fitment for Your GM HD Truck
This module is a direct-fit replacement for the following vehicles equipped with the factory trailer brake control system. We program it specifically for your truck using the VIN you provide at checkout.
- ✔ 2013-2014 GMC Sierra 2500/3500 Pickup & Denali
- ✔ 2013-2014 Chevrolet Silverado 2500/3500 Pickup
- ✔ 2013 GMC Yukon XL 2500
- ✔ 2013 Chevrolet Suburban 2500
Frequently Asked Questions
Do I need to take this part to a dealer to be programmed?
No. The main benefit of our service is that we program the module to your vehicle’s VIN before we ship it. It arrives ready for installation with no further programming required.
What information do you need from me?
After you complete your purchase, you will need to provide us with your vehicle’s 17-digit VIN (Vehicle Identification Number). This ensures we load the correct GM software for your truck’s specific options.
Is this compatible with part number 20850923?
Yes, this module, part number 20964299, is the correct and updated replacement for the older 20850923 part number.
Will this fix the “Service Trailer Brake System” warning?
In the vast majority of cases, a faulty TBCM is the cause of this warning message. Replacing it with this pre-programmed unit is the most common and effective repair.
Where is the TBCM located on my 2013 Yukon XL 2500?
On the 2013 Yukon XL 2500 and Suburban 2500, the module is mounted to the driver’s side frame rail, about halfway down the length of the vehicle.